Medics found insulin had been injected into 36 ampules of the liquid, stored between acute care wards A1 and A3.

All five suspicious deaths happened within the past fortnight, two on the same day.

Rebecca, 27, was arrested on Wednesday in a dawn raid on the flat she shares with fiancé Tim Papworth, 28, above his darts equipment shop.

Detectives were yesterday granted more time to question her.

Tim thanked pals who swamped him and his party-animal partner with messages of support. On his dad Richard’s Facebook page, he wrote: “Thank you all for the support, means so much, love Tim.”

Yesterday new photos emerged of fun-loving Rebecca at a party for fellow nurses. At a separate cowboys and Indians-themed New Year bash she posed with a toy gun in her mouth.

Pal Diane Rothwell posted on Rebecca’s Facebook page: “Becki, the news is totally insane, I do not believe it for 1 second. You would never hurt a fly.”

Former colleague Lindy Gee said: “They need to let u go home immediately with a full apology.”

Last night Rebecca’s mother Lynda, 55, who trains nurses at the hospital, and father David, 60, a coach driver, were not at their home. Assistant Chief Constable Ian Hopkins said the new deaths related to blood sugar levels.

He added: “This is a complex investigation and we are awaiting the results of various tests.”

A report earlier this year revealed a third of drugs that should have been kept locked away at the hospital were not.